1. Field of the Invention
This invention relates to a process for producing aliphatic amines which comprises reacting an aliphatic alcohol or an aliphatic aldehyde with an aminating agent selected from the group consisting of ammonia, a primary amine and a secondary amine in the liquid phase in the presence of an unsupported catalyst consisting essentially of (1) copper oxide or copper hydroxide, (2) nickel oxide or nickel hydroxide and, optionally, (3) an oxide or a hydroxide of a Group II A metal.
2. Description of the Prior Art
The liquid phase amination of long-chain alcohols and aldehydes with ammonia, primary amines or secondary amines is known. The use of copper or nickel catalysts for this reaction is known. Thus, copper has been used as cupric oxide on a refractory support or as a copper chromite catalyst. References such as U.S. Pat. No. 2,160,058 to Covert and French Pat. No. 780,028 disclose the use of copper oxide supported on alumina or silica gel. These references also disclose the use of copper barium chromite as catalysts for the amination reaction. More recently, copper barium chromite catalysts have been employed in U.S. Pat. No. 3,366,687 to Ellis et al. and U.S. Pat. No. 4,138,437 to Strauss et al., while supported copper oxide catalysts have been used in German application No. 2,709,864, U.S. Pat. No. 4,206,150 to Slaugh and U.S. Pat. No. 4,251,465 to Swift et al. Nickel is supplied in the form of Raney nickel in U.S. Pat. No. 2,953,601 to Whitaker, U.S. Pat. No. 3,152,185 to Zvienieka, and U.S. Pat. No. 3,223,734 to Fallstad et al. A nickel-copper-chromia catalyst has been used in U.S. Pat. No. 3,390,184 to Moss et al. In U.S. Pat. No. 4,152,353 Habermann discloses a process employing a catalyst comprising, on an oxide-free basis, 20 to 29 mol percent nickel, 36 to 79 mol percent copper and one to 15 mol percent of a third component selected from iron, zinc, zirconium and mixtures thereof.
Each of the catalysts in the above references exhibited relatively poor activity in the liquid phase amination processes described therein. By "liquid phase" we mean an amination process wherein the alcohol or the aldehyde is in the liquid phase and the ammonia or the primary or secondary amines are in the liquid or gaseous phase under the reaction conditions, defined hereinafter. Thus, large amounts of catalyst, high pressure and/or high temperature are required to achieve reasonable reaction rates. High temperatures and/or high pressures, however, tend to reduce the yield of desired product, while large amounts of catalysts involve higher costs, make filtration more difficult and give rise to additional problems associated with the disposal of spent catalyst. In each of U.S. Pat. Nos. 4,210,605 to Hishino et al. and 4,254,060 to Kimura et al., there is described a homogeneous colloidal catalyst system based on compounds of copper, nickel and barium which are highly active. Although highly active, these catalysts have certain disadvantages. For example, they are highly sensitive to poisons in the feed, and the ligands used can form by-products which can contaminate the amine product. Since these systems are homogeneous, that is, they are colloidally dispersed in the reaction system, they cannot be separated from the reaction product by filtration, but are recovered along with the heavy by-products when the desired amine product is distilled overhead. The number of useful catalyst cycles is therefore limited by the build-up of the associated heavies in the reactor. When the heavy fraction is finally recovered, it is contaminated with the catalyst in colloidal form.